The starting of combustion engines, whether they have applied spark ignition, direct injection or self-ignition, depends on the availability of the starter. The performance of the starter is a function of the size of the vehicle's battery, among other things. The thermal stress of the parts having current flowing through them, and the mechanical load of the parts transmitting the torque, increase with growing battery size. Although the starter is provided for only brief operating periods, one has to expect long cranking times of the combustion engines, especially at lower outside temperatures, and with that, a high thermal stress of the starter.
A starting device for internal combustion engines is described in published German patent document DE 198 10 954. The starting device for internal combustion engines includes a starter motor whose starter pinion is initially engaged with the ring gear of the internal combustion engine via a starter solenoid. After that, the starter motor is operated at maximum torque. Initially, the starter motor drives the pinion at reduced torque via a series resistor. At the same time, the starter solenoid for the starter pinion is pre-engaged at reduced engaging force, e.g., in a clocked manner, with the ring gear and engaged with it when this is indicated. After that, full power is supplied to the starter solenoid, so that the pinion is fully pressed into the ring gear and at the same time a switching contact of a relay, e.g., of the starter solenoid, bridges the series resistor of the starter motor. Now the starter motor is able to crank through the internal combustion engine at full torque.
Published German patent document DE 103 46 857 relates to a device for the protection of a starter line or a starter and generator line in a motor vehicle. The device includes a starter battery, a starter and a starter and generator line or a starter line connecting the starter to the starter battery, a battery disconnect switch being provided in the starter and generator line to which a switch control signal is supplied by a control and regulating unit. The control and regulating unit determines a switch control signal that opens the battery disconnect switch by the evaluation of the measured battery current. In the control and regulating unit, the evaluation of the measured battery current is undertaken while taking into consideration a stored protection characteristics line for the battery current. The stored protection characteristics line includes information about the response of further protection elements of the electrical system of a motor vehicle.
Battery state detection devices are known, within the scope of a motor vehicle electrical system monitoring, in which a metrological recording of electrical quantities and temperatures takes place, using subsequent evaluation by appropriate algorithms for the battery state detection device. Conventional starters of combustion engines are generally designed as DC motors, which are interconnected to the battery via a relay.